This invention relates in general to cushioning devices and more particularly to cushions having a multiplicity of inflatable cells.
Conventional cushioning devices for supporting the human body, such as the typical mattress, seat cushion or padded back rest, do not distribute the weight of the supported body evenly over the area of the body that is in contact with the cushioning device. For example, in the case of a mattress the buttocks or hips, and likewise the shoulders, sink further into the mattress than the lumbar region of the back. Since most conventional cushioning devices exert a supporting force that is proportional to the amount they are deflected, those portions of the body which sink deepest into the cushioning device experience a resisting force per unit area that is considerably greater than those body portions that deflect the cushioning device only slightly. For those individuals who are confined to beds or wheel chairs for extended periods of time the unequal distribution of supporting forces can lead to extreme discomfort and can even be debilitating in the sense that bed sores often develop at the skin areas where the supporting force is greatest.
While cushions which derive their cushioning properties from inner springs or foam material are quite common and inexpensive to manufacture, they suffer the inability to distribute loads or restoring forces evenly. On the other hand, some very specialized cushions are available which distribute the supporting forces more evenly and indeed generally uniformly over the entire supported area. These cushions employ a series of air cells which are extended generally perpendicular from a base and are, therefore, oriented generally perpendicular to the contacting surface of the body that they support. Moreover, all of the cells are interconnected and, therefore, exist at the same internal pressure irrespective of the extent of deflection. Since the ends of the cells actually contact the supported body, it is desirable to have the cells arranged quite closely for this enables the ends of the cells to resemble a generally continuous surface. Perhaps the most refined air cell cushions currently available are disclosed in U.S. Pat. Nos. 3,870,450 and 4,005,236. The air cells of these cushions are molded in a fluted configuration, each with seven or eight fins, so that when the cells are inflated they will expand laterally into contact with each other and their ends will collectively form a generally uniform supporting surface.
While cushions of the type disclosed in U.S. Pat. Nos. 3,870,450 and 4,005,236 provide uniform load supporting characteristics, they are difficult and expensive to manufacture, owing primarily to the large number of fins in each cell. These fins on occasion prevent the latex from distributing uniformly over forms used in the dipping operation by which the cushions are made, and this results in a high rejection rate. The problem seems to reside primarily in the small form radii created by the numerous fins, for air bubbles tend to collect in the radii and cause discontinuities in the latex film that builds up on the form. Also, the numerous fins impede stripping the dipped parts from the forms. Also, the numerous fins on each mold produce an overall cell configuration which tends to experience its greatest wear on the top of the air cell, as well as significant wear along its sides where it contacts other air cells. Furthermore, the cushion, by reason of its multifluted cells, is difficult to clean.